https://sourceware.org/bugzilla/show_bug.cgi?id=29923
Bug ID: 29923
Summary: Renaming symbols with objcopy does not affect the
drectve Section
Product: binutils
Version: 2.39
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: binutils
Assignee: unassigned at sourceware dot org
Reporter: denys.li...@ipg-automotive.com
Target Milestone: ---
Hello everyone,
the following bug report is related to Windows and can be reproduced with the
mingw-w64 toolchain, that is available at:
https://sourceforge.net/projects/mingw-w64/files/Toolchains%20targetting%20Win64/Personal%20Builds/mingw-builds/8.1.0/threads-win32/seh/x86_64-8.1.0-release-win32-seh-rt_v6-rev0.7z/download
A Microsoft Visual Studio installation would be useful as well.
All commands are considered to be done at cmd.exe.
The bug can be reproduced with the following source code:
> // aligned.c
> int aligned_var __attribute__((aligned(32)));
Compile aligned.c, but dont run the linker
> gcc.exe -c -o aligned.o aligned.c
Rename the symbol aligned_var with objcopy
> objcopy.exe --redefine-sym aligned_var=renamed_var aligned.o renamed.o
Verify, that the renaming was successfull:
> nm.exe renamed.o
> 0000000000000000 b .bss
> 0000000000000000 d .data
> 0000000000000000 d .drectve
> 0000000000000000 r .rdata$zzz
> 0000000000000004 C renamed_var
> 0000000000000000 t .text
Unfortunately the renaming does not affect the alignment, that is stored within
the .drectve section. This can be checked with the tool dumpbin.exe, which is
part of MS Visual Studio:
> dumpbin.exe /directives renamed.o
> Microsoft (R) COFF/PE Dumper Version 14.23.28107.0
> Copyright (C) Microsoft Corporation. All rights reserved.
>
> Dump of file renamed.o
>
> File Type: COFF OBJECT
>
> Linker Directives
> -----------------
> -aligncomm:aligned_var,5
>
> Summary
> 0 .bss
> 0 .data
> 1C .drectve
> 20 .rdata$zzz
> 0 .text
As a consequence the linker ignores the alignment for renamed_var in the final
link step.
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